From FactCheck.org: "Clinton charged that Obama’s position has shifted on health care, from favoring a single-payer, universal system when he was a Senate candidate to the plan he favors now, which would provide access to health insurance for all but wouldn’t require it. Obama denied that he had ever said he would work to get a single-payer plan. We score this round for Clinton.
Clinton: Secondly, we have seen once again a kind of evolution here. When Senator Obama ran for the Senate, he was for single-payer and said he was for single-payer if we could get a Democratic president and Democratic Congress. As time went on, the last four or so years, he said he was for single-payer in principle, then he was for universal health care. And then his policy is not, it is not universal. ...
Obama: I never said that we should try to go ahead and get single-payer. What I said was that if I were starting from scratch, if we didn't have a system in which employers had typically provided health care, I would probably go with a single-payer system.
But Obama's denial doesn't hold up. In a speech to the AFL-CIO in 2003, when he was setting up his run for the Senate, Obama said:
Obama (June, 30, 2003): I happen to be a proponent of a single-payer health care program. I see no reason why the United States of America, the wealthiest country in the history of the world, is spending 14 percent, 14 percent, of its gross national product on health care cannot provide basic health insurance to everybody. And that’s what Jim is talking about when he says everybody in, nobody out. A single-payer health care plan, a universal health care plan. And that’s what I’d like to see. And as all of you know, we may not get there immediately. Because first we have to take back the White House, we have to take back the Senate, we have to take back the House.
That sounds to us like someone who's pretty gung-ho for a single-payer plan. But after Democrats captured control of both the House and Senate in 2006, Obama tempered his position. He said in a New Yorker interview last year:
Obama (in The New Yorker, May 7, 2007): If you're starting from scratch, then a single-payer system ... would probably make sense. But we've got all these legacy systems in place, and managing the transition ... would be difficult to pull off. So we may need a system that's not so disruptive.